PROJECT SUMMARY/ABSTRACT Binge drinking is a form of excessive alcohol consumption that is responsible for a number of negative economic and public health outcomes. Repeated episodes of binge drinking result in adaptation in the brain's natural stress/anti-stress circuitry that can promote future alcohol use. The extended amygdala, principally comprised of the central amygdala (CeA) and bed nucleus of the stria terminalis (BNST), is a key regulator of stress response is thought to mediate the negative reinforcing properties of drugs of abuse. Abundant within these brain regions is the kappa opioid receptor (KOR) and its endogenous ligand dynorphin (Dyn), which together have been shown to promote alcohol consumption and negative affective states. Binge-like drinking can be modeled in rodents using Drinking in the Dark (DID) and Intermittent Access (IA) to examine the specific neural circuits involved. Our preliminary results demonstrate that CeA neurons projecting to the BNST show increased excitability following repeated cycles of binge drinking and that chemogenetic inhibition of CeA dynorphin neurons can decrease binge drinking. The goal of the current proposal is thus to mechanistically dissect the effects of repeated binge drinking on dynorphin circuit function and assess how its perturbation may impact future alcohol use. The first set of experiments will use slice electrophysiology to examine how dynorphin transmission in the CeA is altered following three cycles of drinking in the IA paradigm. Next we will use optogenetics and slice electrophysiology to examine alcohol-induced alterations in evoked transmission onto BNST neurons, a major output of CeA dynorphin neurons and a nucleus that has recently been shown to be important for regulating binge alcohol intake. Finally, we will use a novel viral genetic knockdown approach to test the requirement of dynorphin signaling in vivo to mediate excessive drinking behavior. Through this innovative set of experiments, we will obtain a circuit-based model of how binge drinking alters dynorphin transmission in the extended amygdala. This knowledge will be critical for understanding how binge drinking may predispose individuals for future alcohol misuse.